The Capitol Dome, also called the Dome, (PROSE: The Infinity Doctors) was a huge dome which, by many accounts, encased the Capitol. (COMIC: The Tides of Time, The Final Chapter, PROSE: Jealous, Possessive, TV: Gridlock)
By one account, it was constructed by the generation after Rassilon. (PROSE: The Infinity Doctors)
Behind the scenes
The Capitol Dome first appeared in an illustration for the Gallifrey Guardian.